MALAYSIA

Current status

Oyster culture in Malaysia is not well developed with current production being about 10 mt a year (Ng, 1987). Culture experiments were carried out by Okada in the early 1960's (Okada, 1963). Four species of oysters are found in Malaysia: Crassostrea belcheri, C. rivularis, Saccostrea cucullata and Ostrea folium. The first species is the one cultured in the country, while experiments on the culture of the other species are being carried out. C. belcheri are currently being cultured, mostly on a part-time basis, in the Muar River, Johore. In Kedah State culture of the flat oyster (O. folium) is being carried out using the rack and raft culture methods. In Sabah both C. belcheri and S. cucullata are being cultured using the rack method. Oyster culture is also practised on a small scale in the State of Sarawak (Table 7 and Fig. 13).
Oyster production data are available from 1982 to 1984 (Figure 14). Total production of mollusc in Malaysia in 1984 was about 64,080 MT of which 61,650 MT (96.2 %) were from the production of cockle (Anadara granosa), about 1,995 MT (3.0 %) of carpet clam (Paphia undulata), 425 MT (0.66 %) of mussel (Perna viridis) and about 10 MT (1.4 %) of oysters (Crassostrea spp.). While oyster production is low compared to the production of other bivalve species, oyster culture is certainly receiving particular attention from various institutions involved in bivalve work.

Culture practices

Three culture methods are practised in Malaysia. The raft or floating method is employed for oysters grown in riverine conditions where siltation is relatively heavy and tidal range is considerable. The pole and rack methods are intertidal fixed-culture methods used for both spat collection and grow-out.
In Peninsular Malaysia spatfall of most oyster species occurs throughout the year but two main peaks can be distinguished. In the case of oysters in Muar (Johore) and Pulau Langkawi (Kedah) the first peak is generally observed from March to May and the second from September to December. Two peaks are similarly observed for oysters in the States of Sabah and Sarawak: the first from April to June the second from October to November. Spats are usually collected in or in the vicinities of areas where a natural population of parent oysters is present. Monitoring of spatfall is practised by analyzing test collectors placed in various localities. This activity is essential if the bulk of the collectors are to be placed on site without being fouled by barnacles, algae and silt. A variety of collectors either on the bottom or off bottom are used in Malaysia according to the area. In the Muar River, Johore, oyster shells are found to be most suitable for collecting spat of the large oyster, C. belcheri. In Pulau Langkawi polyethylene ropes and nets are used as collectors for the flat oyster O. folium, in Sabah and Sarawak (Eastern Malaysia) corrugated asbestos roofing is the best cultch material (Fig. 15 and Plates 6 and 7)) (Chin and Lim, 1975; Choo, 1983).
The bottom oyster culture method as it is practised in the Muar River requires no special grow-out grounds. Usually the same site is used for collecting the spat and for on-growing. The raft culture method for the flat oyster (O. folium) also requires no grow-out grounds, as the spat are left on the collectors until they reach marketable size. However, thinning is usually necessary when the collectors become too heavy. In Sabah the spats are retained in boxes on racks for about 4–6 months and then removed from the cultch and transferred to trays suspended from rafts (Ng et al., 1982). In Sarawak, collectors are usually transferred from the spatfall areas to more sheltered on-growing grounds. The growth rates of the above oysters vary according to species and locality. C. belcheri cultured in Johore and Sabah attains the commercial size of 12–14 cm after 1 year, whereas the flat oyster O. folium cultured in Pulau Langkawi attains a commercial length of 6–7 cm in 10–12 months. In Sarawak the small oyster S. cucullata attains an average size of 4.5 cm in 1 year, while C. rivularis shows a much faster growth and easily grows to an average length of 7.5 cm in 1 year.
Harvesting is carried out manually. No mechanical devices (dredges) have been introduced in the areas where bottom culture is practised because of the fear of damaging the oyster beds. Only oysters of marketable size are collected.

Problems and constraints

The main constraints affecting oyster culture in Peninsular Malaysia are fouling from other sedentary organisms and algae, predation by xanthid crabs (Myomenippe granulosa) and starfish, siltation as well as relatively poor spatfalls in some areas.
The lack of sanitation measures is an increasing concern within the bivalve industry in general. Presently no sanitation control measures are strictly enforced to ensure the quality of cultured bivalves.

Future plans

Oyster culture in Peninsular Malaysia is still in the initial stages of development and there is a considerable number of problems to be resolved before the commercial culture of oysters can be carried out. Further research into adapting established culture methods from countries in the region as well as identifying further suitable sites will certainly help towards the commercial propagation of oysters in Malaysia.
Research efforts on oyster culture techniques and identification of potential sites are underway (under BOBP funding) and it is hoped that the information gathered will enable further development and proper management of this resource.
With regard to bivalve purification a suitable system is being developed with inputs from ASEAN/Canada and ASEAN/Australia.
In Sabah and Sarawak, studies are concentrated on the further development of culture techniques and on the economic aspects of oyster culture.

Table 7. Distribution and main culture areas of commercially important oyster species in Malaysia.

Figure 13: Major farming areas of the four commercially important oyster species in Malaysia.

Figure 14: Oyster production data in Malaysia from 1982 to 1984. (Source: Ng, F. O., 1987).

Figure 15: Corrugated asbestos sheets on racks for spat collection.

Plate 4: Young oysters (2–5 cm shell length) attached on asbestos sheets.

Plate 5: Separation of young oysters from asbestos sheets.